4,060 research outputs found
Evolution of vacancy pores in bounded particles
In the present work, the behavior of vacancy pore inside of spherical
particle is investigated. On the assumption of quasistationarity of diffusion
fluxes, the nonlinear equation set was obtained analytically, that describes
completely pore behavior inside of spherical particle. Limiting cases of small
and large pores are considered. The comparison of numerical results with
asymptotic behavior of considered limiting cases of small and large pores is
discussed.Comment: 25 pages, 10 figure
Electronic properties of LaAlO3/SrTiO3 n-type interfaces: A GGA+U study
The role of electronic correlation effects for a realistic description of the
electronic properties of LaAlO3/SrTiO3 heterostructures as covered by the
on-site Coulomb repulsion within the GGA+U approach is investigated. Performing
a systematic variation of the values of the Coulomb parameters applied to the
Ti 3d and La 4f orbitals we put previous suggestions to include a large value
for the La 4f states into perspective. Furthermore, our calculations provide
deeper insight into the band gap landscape in the space spanned by these
Coulomb parameters and the resulting complex interference effects. In addition,
we identify important correlations between the local Coulomb interaction within
the La 4f shell, the band gap, and the atomic displacements at the interface.
In particular, these on-site Coulomb interactions influence buckling within the
LaO interface layer, which via its strong coupling to the electrostatic
potential in the LAO overlayer causes considerable shifts of the electronic
states at the surface and eventually controls the band gap.Comment: 14 pages, 9 figure
Orbital Ordering and Spin-Ladder Formation in La2RuO5
The semiconductor-semiconductor transition of La2RuO5 is studied by means of
augmented spherical wave (ASW) electronic structure calculations as based on
density functional theory and the local density approximation. This transition
has lately been reported to lead to orbital ordering and a quenching of the
local spin magnetic moment. Our results hint towards an orbital ordering
scenario which, markedly different from the previously proposed scheme,
preserves the local S = 1 moment at the Ru sites in the low-temperature phase.
The unusual magnetic behaviour is interpreted by the formation of spin-ladders,
which result from the structural changes occurring at the transition and are
characterized by antiferromagnetic coupling along the rungs.Comment: 5 pages, 4 figures, for more information see
http://www.physik.uni-augsburg.de/~eyert
Superconducting Junctions with Ferromagnetic, Antiferromagnetic or Charge-Density-Wave Interlayers
Spectra and spin structures of Andreev interface states and the Josephson
current are investigated theoretically in junctions between clean
superconductors (SC) with ordered interlayers. The Josephson current through
the ferromagnet-insulator-ferromagnet interlayer can exhibit a nonmonotonic
dependence on the misorientation angle. The characteristic behavior takes place
if the pi state is the equilibrium state of the junction in the particular case
of parallel magnetizations. We find a novel channel of quasiparticle reflection
(Q reflection) from the simplest two-sublattice antiferromagnet (AF) on a
bipartite lattice. As a combined effect of Andreev and Q reflections, Andreev
states arise at the AF/SC interface. When the Q reflection dominates the
specular one, Andreev bound states have almost zero energy on AF/ s-wave SC
interfaces, whereas they lie near the edge of the continuous spectrum for
AF/d-wave SC boundaries. For an s-wave SC/AF/s-wave SC junction, the bound
states are found to split and carry the supercurrent. Our analytical results
are based on a novel quasiclassical approach, which applies to interfaces
involving itinerant antiferromagnets. Similar effects can take place on
interfaces of superconductors with charge density wave materials (CDW),
including the possible d-density wave state (DDW) of the cuprates.Comment: LT24 conference proceeding, 2 pages, 1 figur
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